How to format excel columns if already formated as text in c++?

See more:

C++

I created an excel automation application.
I start Excel, create a Workbook, create a Worksheet and fill a range with data.
Excel assumes text data in columns even if they are filled with numbers.
How can I format the column or range as numbers?
or
Where can I find more Information about the subject? I need a link or article No.

Thanks in forward
Abzadeh